The use of elastomeric discs to control flow rates as a result of increased pressure is well-known. Elastomeric discs are positioned over apertures which enable the control of flow rate of water past the disc as the pressure increases due to flexing of the disc. Ordinarily, the disc is positioned over a recess and has a water passageway which is progressively reduced in diameter as the disc flexes further into the recess.
There are variations on the shape of the apertures within which the disc flexes into, but the main principle of operation is the continual reduction in flow passage diameter as the pressure increases.
The main reason for using pressure compensators on irrigation equipment is to ensure that each sprinkler discharges at substantially the same volume flow rate. Supply pressure along a distribution line can vary considerably due to friction losses, resulting in a significantly lower pressure at the end of a long run. In addition, irrigation lines installed on a slope with a significant height variation from one end to the other will also suffer considerable pressure variations along the line. This would result in some areas of a crop receiving more water than others unless some form of pressure compensation is used.
Most pressure compensators using an elastomeric disc rely on tension in the disc resulting from flexion to form a concave shape. In order to achieve flow control at low pressures, a relatively large diameter disc of thin material is required. This results in tensions which are considerably less by comparison to smaller diameter discs.
However, a disadvantage with the use of large diameter discs is the fact that they require large diameter sprinkler bodies. This is not always desirable, and in some instances it may be essential to make use of a smaller diameter elastomeric disc.
Accordingly, it is an object of this invention to provide a means of better flow control at lower pressures, and to also provide a means of flow control which would be suited to smaller elastomeric compensating discs.
A further problem with existing pressure compensators is blockage and the difficulty in removing blockages. When the water supply is turned off, the elastomeric disc flattens so that the initial water flow, when it is next turned on, will flush away any blockages. However, the channels are often very small and therefore do not flush adequately.
Also, the use of such small channels requires a great degree of accuracy in manufacture to ensure consistent flow control.
It is a further aspect of the invention to overcome the above problems.